# Licensed under the LGPL: https://www.gnu.org/licenses/old-licenses/lgpl-2.1.en.html
# For details: https://github.com/pylint-dev/astroid/blob/main/LICENSE
# Copyright (c) https://github.com/pylint-dev/astroid/blob/main/CONTRIBUTORS.txt
"""This module contains base classes and functions for the nodes and some
inference utils.
"""
from __future__ import annotations
import collections
import collections.abc
from collections.abc import Iterable, Iterator
from typing import TYPE_CHECKING, Any, Literal
from astroid import decorators, nodes
from astroid.const import PY311_PLUS
from astroid.context import (
CallContext,
InferenceContext,
bind_context_to_node,
copy_context,
)
from astroid.exceptions import (
AstroidTypeError,
AttributeInferenceError,
InferenceError,
NameInferenceError,
)
from astroid.interpreter import objectmodel
from astroid.typing import (
InferenceErrorInfo,
InferenceResult,
SuccessfulInferenceResult,
)
from astroid.util import Uninferable, UninferableBase, safe_infer
if TYPE_CHECKING:
from astroid.constraint import Constraint
PROPERTIES = {"builtins.property", "abc.abstractproperty", "functools.cached_property"}
# enum.property was added in Python 3.11
if PY311_PLUS:
PROPERTIES.add("enum.property")
# List of possible property names. We use this list in order
# to see if a method is a property or not. This should be
# pretty reliable and fast, the alternative being to check each
# decorator to see if its a real property-like descriptor, which
# can be too complicated.
# Also, these aren't qualified, because each project can
# define them, we shouldn't expect to know every possible
# property-like decorator!
POSSIBLE_PROPERTIES = {
"cached_property",
"cachedproperty",
"lazyproperty",
"lazy_property",
"reify",
"lazyattribute",
"lazy_attribute",
"LazyProperty",
"lazy",
"cache_readonly",
"DynamicClassAttribute",
}
def _is_property(
meth: nodes.FunctionDef | UnboundMethod, context: InferenceContext | None = None
) -> bool:
decoratornames = meth.decoratornames(context=context)
if PROPERTIES.intersection(decoratornames):
return True
stripped = {
name.split(".")[-1]
for name in decoratornames
if not isinstance(name, UninferableBase)
}
if any(name in stripped for name in POSSIBLE_PROPERTIES):
return True
if not meth.decorators:
return False
# Lookup for subclasses of *property*
for decorator in meth.decorators.nodes or ():
inferred = safe_infer(decorator, context=context)
if inferred is None or isinstance(inferred, UninferableBase):
continue
if isinstance(inferred, nodes.ClassDef):
# Check for a class which inherits from a standard property type
if any(inferred.is_subtype_of(pclass) for pclass in PROPERTIES):
return True
for base_class in inferred.bases:
# Check for a class which inherits from functools.cached_property
# and includes a subscripted type annotation
if isinstance(base_class, nodes.Subscript):
value = safe_infer(base_class.value, context=context)
if not isinstance(value, nodes.ClassDef):
continue
if value.name != "cached_property":
continue
module, _ = value.lookup(value.name)
if isinstance(module, nodes.Module) and module.name == "functools":
return True
continue
return False
class Proxy:
"""A simple proxy object.
Note:
Subclasses of this object will need a custom __getattr__
if new instance attributes are created. See the Const class
"""
_proxied: nodes.ClassDef | nodes.FunctionDef | nodes.Lambda | UnboundMethod
def __init__(
self,
proxied: (
nodes.ClassDef | nodes.FunctionDef | nodes.Lambda | UnboundMethod | None
) = None,
) -> None:
if proxied is None:
# This is a hack to allow calling this __init__ during bootstrapping of
# builtin classes and their docstrings.
# For Const, Generator, and UnionType nodes the _proxied attribute
# is set during bootstrapping
# as we first need to build the ClassDef that they can proxy.
# Thus, if proxied is None self should be a Const or Generator
# as that is the only way _proxied will be correctly set as a ClassDef.
assert isinstance(self, (nodes.Const, Generator, UnionType))
else:
self._proxied = proxied
def __getattr__(self, name: str) -> Any:
if name == "_proxied":
return self.__class__._proxied
if name in self.__dict__:
return self.__dict__[name]
return getattr(self._proxied, name)
def infer( # type: ignore[return]
self, context: InferenceContext | None = None, **kwargs: Any
) -> collections.abc.Generator[InferenceResult, None, InferenceErrorInfo | None]:
yield self
def _infer_stmts(
stmts: Iterable[InferenceResult],
context: InferenceContext | None,
frame: nodes.NodeNG | BaseInstance | None = None,
) -> collections.abc.Generator[InferenceResult]:
"""Return an iterator on statements inferred by each statement in *stmts*."""
inferred = False
constraint_failed = False
if context is not None:
name = context.lookupname
context = context.clone()
if name is not None:
constraints = context.constraints.get(name, {})
else:
constraints = {}
else:
name = None
constraints = {}
context = InferenceContext()
for stmt in stmts:
if isinstance(stmt, UninferableBase):
yield stmt
inferred = True
continue
context.lookupname = stmt._infer_name(frame, name)
try:
stmt_constraints: set[Constraint] = set()
for constraint_stmt, potential_constraints in constraints.items():
if not constraint_stmt.parent_of(stmt):
stmt_constraints.update(potential_constraints)
for inf in stmt.infer(context=context):
if all(
constraint.satisfied_by(inf, context)
for constraint in stmt_constraints
):
yield inf
inferred = True
else:
constraint_failed = True
except NameInferenceError:
continue
except InferenceError:
yield Uninferable
inferred = True
if not inferred and constraint_failed:
yield Uninferable
elif not inferred:
raise InferenceError(
"Inference failed for all members of {stmts!r}.",
stmts=stmts,
frame=frame,
context=context,
)
def _infer_method_result_truth(
instance: Instance, method_name: str, context: InferenceContext
) -> bool | UninferableBase:
# Get the method from the instance and try to infer
# its return's truth value.
meth = next(instance.igetattr(method_name, context=context), None)
if meth and hasattr(meth, "infer_call_result"):
if not meth.callable():
return Uninferable
try:
context.callcontext = CallContext(args=[], callee=meth)
for value in meth.infer_call_result(instance, context=context):
if isinstance(value, UninferableBase):
return value
try:
inferred = next(value.infer(context=context))
except StopIteration as e:
raise InferenceError(context=context) from e
return inferred.bool_value()
except InferenceError:
pass
return Uninferable
[docs]
class BaseInstance(Proxy):
"""An instance base class, which provides lookup methods for potential
instances.
"""
_proxied: nodes.ClassDef
special_attributes: objectmodel.ObjectModel
[docs]
def display_type(self) -> str:
return "Instance of"
[docs]
def getattr(
self,
name: str,
context: InferenceContext | None = None,
lookupclass: bool = True,
) -> list[InferenceResult]:
try:
values = self._proxied.instance_attr(name, context)
except AttributeInferenceError as exc:
if self.special_attributes and name in self.special_attributes:
special_attr = self.special_attributes.lookup(name)
if not isinstance(special_attr, nodes.Unknown):
return [special_attr]
if lookupclass:
# Class attributes not available through the instance
# unless they are explicitly defined.
return self._proxied.getattr(name, context, class_context=False)
raise AttributeInferenceError(
target=self, attribute=name, context=context
) from exc
# since we've no context information, return matching class members as
# well
if lookupclass:
try:
return values + self._proxied.getattr(
name, context, class_context=False
)
except AttributeInferenceError:
pass
return values
[docs]
def igetattr(
self, name: str, context: InferenceContext | None = None
) -> Iterator[InferenceResult]:
"""Inferred getattr."""
if not context:
context = InferenceContext()
try:
context.lookupname = name
# XXX frame should be self._proxied, or not ?
get_attr = self.getattr(name, context, lookupclass=False)
yield from _infer_stmts(
self._wrap_attr(get_attr, context), context, frame=self
)
except AttributeInferenceError:
try:
# fallback to class.igetattr since it has some logic to handle
# descriptors
# But only if the _proxied is the Class.
if self._proxied.__class__.__name__ != "ClassDef":
raise
attrs = self._proxied.igetattr(name, context, class_context=False)
yield from self._wrap_attr(attrs, context)
except AttributeInferenceError as error:
raise InferenceError(**vars(error)) from error
def _wrap_attr(
self, attrs: Iterable[InferenceResult], context: InferenceContext | None = None
) -> Iterator[InferenceResult]:
"""Wrap bound methods of attrs in a InstanceMethod proxies."""
for attr in attrs:
if isinstance(attr, UnboundMethod):
if _is_property(attr):
yield from attr.infer_call_result(self, context)
else:
yield BoundMethod(attr, self)
elif isinstance(attr, nodes.Lambda):
if attr.args.arguments and attr.args.arguments[0].name == "self":
yield BoundMethod(attr, self)
continue
yield attr
else:
yield attr
[docs]
def infer_call_result(
self,
caller: SuccessfulInferenceResult | None,
context: InferenceContext | None = None,
) -> Iterator[InferenceResult]:
"""Infer what a class instance is returning when called."""
context = bind_context_to_node(context, self)
inferred = False
# If the call is an attribute on the instance, we infer the attribute itself
if isinstance(caller, nodes.Call) and isinstance(caller.func, nodes.Attribute):
for res in self.igetattr(caller.func.attrname, context):
inferred = True
yield res
# Otherwise we infer the call to the __call__ dunder normally
for node in self._proxied.igetattr("__call__", context):
if isinstance(node, UninferableBase) or not node.callable():
continue
if isinstance(node, BaseInstance) and node._proxied is self._proxied:
inferred = True
yield node
# Prevent recursion.
continue
for res in node.infer_call_result(caller, context):
inferred = True
yield res
if not inferred:
raise InferenceError(node=self, caller=caller, context=context)
[docs]
class Instance(BaseInstance):
"""A special node representing a class instance."""
special_attributes = objectmodel.InstanceModel()
def __init__(self, proxied: nodes.ClassDef | None) -> None:
super().__init__(proxied)
@decorators.yes_if_nothing_inferred
def infer_binary_op(
self,
opnode: nodes.AugAssign | nodes.BinOp,
operator: str,
other: InferenceResult,
context: InferenceContext,
method: SuccessfulInferenceResult,
) -> Generator[InferenceResult]:
return method.infer_call_result(self, context)
def __repr__(self) -> str:
return "<Instance of {}.{} at 0x{}>".format(
self._proxied.root().name, self._proxied.name, id(self)
)
def __str__(self) -> str:
return f"Instance of {self._proxied.root().name}.{self._proxied.name}"
[docs]
def callable(self) -> bool:
try:
self._proxied.getattr("__call__", class_context=False)
return True
except AttributeInferenceError:
return False
[docs]
def pytype(self) -> str:
return self._proxied.qname()
[docs]
def display_type(self) -> str:
return "Instance of"
[docs]
def bool_value(
self, context: InferenceContext | None = None
) -> bool | UninferableBase:
"""Infer the truth value for an Instance.
The truth value of an instance is determined by these conditions:
* if it implements __bool__ on Python 3 or __nonzero__
on Python 2, then its bool value will be determined by
calling this special method and checking its result.
* when this method is not defined, __len__() is called, if it
is defined, and the object is considered true if its result is
nonzero. If a class defines neither __len__() nor __bool__(),
all its instances are considered true.
"""
context = context or InferenceContext()
context.boundnode = self
try:
result = _infer_method_result_truth(self, "__bool__", context)
except (InferenceError, AttributeInferenceError):
# Fallback to __len__.
try:
result = _infer_method_result_truth(self, "__len__", context)
except (AttributeInferenceError, InferenceError):
return True
return result
[docs]
def getitem(
self, index: nodes.Const, context: InferenceContext | None = None
) -> InferenceResult | None:
new_context = bind_context_to_node(context, self)
if not context:
context = new_context
method = next(self.igetattr("__getitem__", context=context), None)
# Create a new CallContext for providing index as an argument.
new_context.callcontext = CallContext(args=[index], callee=method)
if not isinstance(method, BoundMethod):
raise InferenceError(
"Could not find __getitem__ for {node!r}.", node=self, context=context
)
if len(method.args.arguments) != 2: # (self, index)
raise AstroidTypeError(
"__getitem__ for {node!r} does not have correct signature",
node=self,
context=context,
)
return next(method.infer_call_result(self, new_context), None)
[docs]
class UnboundMethod(Proxy):
"""A special node representing a method not bound to an instance."""
_proxied: nodes.FunctionDef | UnboundMethod
special_attributes: (
objectmodel.BoundMethodModel | objectmodel.UnboundMethodModel
) = objectmodel.UnboundMethodModel()
def __repr__(self) -> str:
assert self._proxied.parent, "Expected a parent node"
frame = self._proxied.parent.frame()
return "<{} {} of {} at 0x{}".format(
self.__class__.__name__, self._proxied.name, frame.qname(), id(self)
)
[docs]
def implicit_parameters(self) -> Literal[0, 1]:
return 0
[docs]
def is_bound(self) -> bool:
return False
[docs]
def getattr(self, name: str, context: InferenceContext | None = None):
if name in self.special_attributes:
special_attr = self.special_attributes.lookup(name)
if not isinstance(special_attr, nodes.Unknown):
return [special_attr]
return self._proxied.getattr(name, context)
[docs]
def igetattr(
self, name: str, context: InferenceContext | None = None
) -> Iterator[InferenceResult]:
if name in self.special_attributes:
special_attr = self.special_attributes.lookup(name)
if not isinstance(special_attr, nodes.Unknown):
return iter((special_attr,))
return self._proxied.igetattr(name, context)
[docs]
def infer_call_result(
self,
caller: SuccessfulInferenceResult | None,
context: InferenceContext | None = None,
) -> Iterator[InferenceResult]:
"""
The boundnode of the regular context with a function called
on ``object.__new__`` will be of type ``object``,
which is incorrect for the argument in general.
If no context is given the ``object.__new__`` call argument will
be correctly inferred except when inside a call that requires
the additional context (such as a classmethod) of the boundnode
to determine which class the method was called from
"""
# If we're unbound method __new__ of a builtin, the result is an
# instance of the class given as first argument.
if self._proxied.name == "__new__":
assert self._proxied.parent, "Expected a parent node"
qname = self._proxied.parent.frame().qname()
# Avoid checking builtins.type: _infer_type_new_call() does more validation
if qname.startswith("builtins.") and qname != "builtins.type":
return self._infer_builtin_new(caller, context or InferenceContext())
return self._proxied.infer_call_result(caller, context)
def _infer_builtin_new(
self,
caller: SuccessfulInferenceResult | None,
context: InferenceContext,
) -> collections.abc.Generator[nodes.Const | Instance | UninferableBase]:
if not isinstance(caller, nodes.Call):
return
if not caller.args:
return
# Attempt to create a constant
if len(caller.args) > 1:
value = None
if isinstance(caller.args[1], nodes.Const):
value = caller.args[1].value
else:
inferred_arg = next(caller.args[1].infer(), None)
if isinstance(inferred_arg, nodes.Const):
value = inferred_arg.value
if value is not None:
const = nodes.const_factory(value)
assert not isinstance(const, nodes.EmptyNode)
yield const
return
node_context = context.extra_context.get(caller.args[0])
for inferred in caller.args[0].infer(context=node_context):
if isinstance(inferred, UninferableBase):
yield inferred
if isinstance(inferred, nodes.ClassDef):
yield Instance(inferred)
raise InferenceError
[docs]
def bool_value(self, context: InferenceContext | None = None) -> Literal[True]:
return True
[docs]
class BoundMethod(UnboundMethod):
"""A special node representing a method bound to an instance."""
special_attributes = objectmodel.BoundMethodModel()
def __init__(
self,
proxy: nodes.FunctionDef | nodes.Lambda | UnboundMethod,
bound: SuccessfulInferenceResult,
original_caller: SuccessfulInferenceResult | None = None,
) -> None:
super().__init__(proxy)
self.bound = bound
# For super() calls: the actual instance/class that called super()
# Used to correctly infer return type of methods returning Self
self.original_caller = original_caller
[docs]
def implicit_parameters(self) -> Literal[0, 1]:
if self.name == "__new__":
# __new__ acts as a classmethod but the class argument is not implicit.
return 0
return 1
[docs]
def is_bound(self) -> Literal[True]:
return True
def _infer_type_new_call(
self, caller: nodes.Call, context: InferenceContext
) -> nodes.ClassDef | None: # noqa: C901
"""Try to infer what type.__new__(mcs, name, bases, attrs) returns.
In order for such call to be valid, the metaclass needs to be
a subtype of ``type``, the name needs to be a string, the bases
needs to be a tuple of classes
"""
# pylint: disable=import-outside-toplevel; circular import
from astroid.nodes import Pass
# Verify the metaclass
try:
mcs = next(caller.args[0].infer(context=context))
except StopIteration as e:
raise InferenceError(context=context) from e
if not isinstance(mcs, nodes.ClassDef):
# Not a valid first argument.
raise InferenceError(
"type.__new__() requires a class for metaclass", context=context
)
if not mcs.is_subtype_of("builtins.type"):
# Not a valid metaclass.
raise InferenceError(
"type.__new__() metaclass must be a subclass of type", context=context
)
# Verify the name
try:
name = next(caller.args[1].infer(context=context))
except StopIteration as e:
raise InferenceError(context=context) from e
if not isinstance(name, nodes.Const):
# Not a valid name, needs to be a const.
raise InferenceError(
"type.__new__() requires a constant for name", context=context
)
if not isinstance(name.value, str):
# Needs to be a string.
raise InferenceError(
"type.__new__() requires a string for name", context=context
)
# Verify the bases
try:
bases = next(caller.args[2].infer(context=context))
except StopIteration as e:
raise InferenceError(context=context) from e
if not isinstance(bases, nodes.Tuple):
# Needs to be a tuple.
raise InferenceError(
"type.__new__() requires a tuple for bases", context=context
)
try:
inferred_bases = [next(elt.infer(context=context)) for elt in bases.elts]
except StopIteration as e:
raise InferenceError(context=context) from e
if any(not isinstance(base, nodes.ClassDef) for base in inferred_bases):
# All the bases needs to be Classes
raise InferenceError(
"type.__new__() requires classes for bases", context=context
)
# Verify the attributes.
try:
attrs = next(caller.args[3].infer(context=context))
except StopIteration as e:
raise InferenceError(context=context) from e
if not isinstance(attrs, nodes.Dict):
# Needs to be a dictionary.
raise InferenceError(
"type.__new__() requires a dict for attrs", context=context
)
cls_locals: dict[str, list[InferenceResult]] = collections.defaultdict(list)
for key, value in attrs.items:
try:
key = next(key.infer(context=context))
except StopIteration as e:
raise InferenceError(context=context) from e
try:
value = next(value.infer(context=context))
except StopIteration as e:
raise InferenceError(context=context) from e
# Ignore non string keys
if isinstance(key, nodes.Const) and isinstance(key.value, str):
cls_locals[key.value].append(value)
# Build the class from now.
cls = mcs.__class__(
name=name.value,
lineno=caller.lineno or 0,
col_offset=caller.col_offset or 0,
parent=caller,
end_lineno=caller.end_lineno,
end_col_offset=caller.end_col_offset,
)
empty = Pass(
parent=cls,
lineno=caller.lineno,
col_offset=caller.col_offset,
end_lineno=caller.end_lineno,
end_col_offset=caller.end_col_offset,
)
cls.postinit(
bases=bases.elts,
body=[empty],
decorators=None,
newstyle=True,
metaclass=mcs,
keywords=[],
)
cls.locals = cls_locals
return cls
[docs]
def infer_call_result(
self,
caller: SuccessfulInferenceResult | None,
context: InferenceContext | None = None,
) -> Iterator[InferenceResult]:
# For super() calls, use original_caller to correctly infer Self return type
bound_node = self.original_caller if self.original_caller else self.bound
context = bind_context_to_node(context, bound_node)
if (
isinstance(self.bound, nodes.ClassDef)
and self.bound.name == "type"
and self.name == "__new__"
and isinstance(caller, nodes.Call)
):
# Check if we have a ``type.__new__(mcs, name, bases, attrs)`` call.
if len(caller.args) != 4:
raise InferenceError(
f"type.__new__() requires 4 arguments, got {len(caller.args)}",
context=context,
)
new_cls = self._infer_type_new_call(caller, context)
if new_cls:
return iter((new_cls,))
return super().infer_call_result(caller, context)
[docs]
def bool_value(self, context: InferenceContext | None = None) -> Literal[True]:
return True
class Generator(BaseInstance):
"""A special node representing a generator.
Proxied class is set once for all in raw_building.
"""
# We defer initialization of special_attributes to the __init__ method since the constructor
# of GeneratorModel requires the raw_building to be complete
# TODO: This should probably be refactored.
special_attributes: objectmodel.GeneratorBaseModel
def __init__(
self,
parent: nodes.FunctionDef,
generator_initial_context: InferenceContext | None = None,
) -> None:
super().__init__()
self.parent = parent
self._call_context = copy_context(generator_initial_context)
# See comment above: this is a deferred initialization.
Generator.special_attributes = objectmodel.GeneratorModel()
def infer_yield_types(self) -> Iterator[InferenceResult]:
yield from self.parent.infer_yield_result(self._call_context)
def callable(self) -> Literal[False]:
return False
def pytype(self) -> str:
return "builtins.generator"
def display_type(self) -> str:
return "Generator"
def bool_value(self, context: InferenceContext | None = None) -> Literal[True]:
return True
def __repr__(self) -> str:
return f"<Generator({self._proxied.name}) l.{self.lineno} at 0x{id(self)}>"
def __str__(self) -> str:
return f"Generator({self._proxied.name})"
class AsyncGenerator(Generator):
"""Special node representing an async generator."""
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
AsyncGenerator.special_attributes = objectmodel.AsyncGeneratorModel()
def pytype(self) -> Literal["builtins.async_generator"]:
return "builtins.async_generator"
def display_type(self) -> str:
return "AsyncGenerator"
def __repr__(self) -> str:
return f"<AsyncGenerator({self._proxied.name}) l.{self.lineno} at 0x{id(self)}>"
def __str__(self) -> str:
return f"AsyncGenerator({self._proxied.name})"
class UnionType(BaseInstance):
"""Special node representing new style typing unions.
Proxied class is set once for all in raw_building.
"""
def __init__(
self,
left: UnionType | nodes.ClassDef | nodes.Const,
right: UnionType | nodes.ClassDef | nodes.Const,
parent: nodes.NodeNG | None = None,
) -> None:
super().__init__()
self.parent = parent
self.left = left
self.right = right
def callable(self) -> Literal[False]:
return False
def bool_value(self, context: InferenceContext | None = None) -> Literal[True]:
return True
def pytype(self) -> Literal["types.UnionType"]:
return "types.UnionType"
def display_type(self) -> str:
return "UnionType"
def __repr__(self) -> str:
return f"<UnionType({self._proxied.name}) l.{self.lineno} at 0x{id(self)}>"
def __str__(self) -> str:
return f"UnionType({self._proxied.name})"